A typical method of providing steering stability performance on both a dry road surface and on a wet road surface involves, for a tire mounted on a vehicle, improving pattern rigidity in a tire circumferential direction on a vehicle outer side of a tire equatorial plane, and relatively enlarging a groove surface area and volume on a vehicle inner side. Such a method does enable the steering stability performance to be provided on both the dry road surface and the wet road surface. However, bringing out the maximum potential of the vehicle while improving the performance of the vehicle requires that the steering stability performance on both the dry road surface and on the wet road surface be achieved to a high degree. As such, the development of a pneumatic tire mount method and a combination pneumatic tire suitable for the vehicle is desired.
A pneumatic tire mount method and a pneumatic tire for a front wheel described in Japanese Unexamined Patent Application Publication No. 2002-274120A aim to improve braking performance. Japanese Unexamined Patent Application Publication No. 2002-274120A describes an installation method of a pneumatic tire of using a pneumatic tire which rigidity in the circumferential direction per unit area of a tread pattern is set so as to be greater in a region other than a region on opposite side of a tire equatorial surface, wherein the region larger in rigidity in the circumferential direction is arranged on the vehicle inner side for at least the front wheel of the vehicle. Also, Japanese Unexamined Patent Application Publication No. 2002-274120A describes a pneumatic tire for a front wheel in which the rigidity in the circumferential direction per unit area of the tread pattern varies in left and right regions of the tire equatorial surface. In the pneumatic tire for the front wheel, the rigidity of the tread pattern in a region on the installation inside of the vehicle is greater than the rigidity of the tread pattern in a region on the installation outside of the vehicle.
A motor vehicle and combination of front wheel and rear wheel pneumatic tires used therefor described in Japanese Unexamined Patent Application Publication No. 2000-158908A aim to shorten the braking distance. Japanese Unexamined Patent Application Publication No. 2000-158908A describes a motor vehicle equipped with front wheel and rear wheel pneumatic tires. Each pneumatic tire is provided with a plurality of land portions partitioned by a tread groove. The rear wheel pattern rigidity, which is the sum of the circumferential rigidity of each land portion on the pneumatic tire of the rear wheel, is greater than the front wheel pattern rigidity, which is the sum of the circumferential rigidity of each land portion on the pneumatic tire of the front wheel.
A pneumatic radial tire for a rear wheel drive type automobile described in Japanese Unexamined Patent Application Publication No. H11-245621A aims to improve the traveling stability on a dry road surface without lowering the water discharging performance on a wet road surface. Japanese Unexamined Patent Application Publication No. H11-245621A describes a pneumatic tire having a directional tread pattern provided with a circumferential direction groove extending continuously in parallel to or substantially parallel to a tire circumferential direction, and with a plurality of directional diagonal grooves extending in a direction that is diagonal with respect to the tire circumferential direction and arranged with equal spacing in the tire circumferential direction. Upon mounting on the front wheels and rear wheels of the same vehicle for use as a set, a tire installing axle at the time of installing on the vehicle is specified, a tire formed with a tread pattern having a relatively large negative ratio is set for a front wheel tire, and a tire formed with a tread pattern having a relatively small negative ratio is set for a rear wheel tire.
A combination tire for a four-wheel passenger car and its mounting method described in Japanese Unexamined Patent Application Publication No. H11-139108A aim to improve hydro-planing preventing performance during forward movement while suppressing noise at the time of passing. Japanese Unexamined Patent Application Publication No. H11-139108A describes mounting a tire provided with a plurality of circumferential main grooves extended in the circumferential direction of the tread on two front wheels, and mounting a tire having a directional pattern provided with a plurality of inclined main grooves inclined to the outside of the tire from a center part toward an opposite direction, replacing the circumferential main grooves on the tread, to a rotating direction on two rear wheels.